Generation, transmission, and conversion of orbital torque by an antiferromagnetic insulator

Shilei Ding (), Paul Noël, Gunasheel Kauwtilyaa Krishnaswamy, Niccolò Davitti, Giacomo Sala, Marzia Fantauzzi, Antonella Rossi and Pietro Gambardella ()
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Shilei Ding: ETH Zürich
Paul Noël: ETH Zürich
Gunasheel Kauwtilyaa Krishnaswamy: ETH Zürich
Niccolò Davitti: ETH Zürich
Giacomo Sala: ETH Zürich
Marzia Fantauzzi: Campus di Monserrato, Università degli Studi di Cagliari
Antonella Rossi: ETH Zürich
Pietro Gambardella: ETH Zürich

Nature Communications, 2025, vol. 16, issue 1, 1-10

Abstract: Abstract Electrical control of magnetization in nanoscale devices can be significantly improved through the efficient generation of orbital currents and their conversion into spin currents. In nonmagnetic/ferromagnetic bilayers, this conversion produces a torque on the magnetization, enabling magnetization switching and dynamic manipulation. While previous studies focus on metallic ferromagnets, we demonstrate a large orbital torque and enhanced orbital-to-spin conversion by an antiferromagnetic insulating CoO layer. Measurements in CuOx/CoO/Co trilayers show that inserting CoO reverses the torque’s sign and triples its magnitude compared to CuOx/Co. This behaviour stems from the inverted oxygen gradient at the CuOx/CoO interface and CoO’s high orbital multiplicity, which favours the transmission of orbital momenta and efficient orbital-to-spin conversion. At low temperatures, the onset of antiferromagnetic order induces a further many-fold increase of the torque, which we attribute to the efficient excitation and propagation of spin-orbit excitons induced by magnetic coupling. Comparative measurements of CuOx/NiO/Co and CuOx/MnO/Co trilayers show that the torque efficiency scales with the orbital momentum of the Co2+, Ni2+, and Mn2+ ions in the antiferromagnet. These results reveal that antiferromagnetic insulators like CoO provide highly effective orbital-to-spin transduction, combining orbital torque and exchange bias functionalities to improve the performance of spintronic devices.

Date: 2025
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DOI: 10.1038/s41467-025-64273-6

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